1. Field of the Invention
The present invention relates to the process for producing pyrogallol and 5-substituted pyrogallol.
2. Description of the Prior Art
Pyrogallol has been produced conventionally by decarboxylation of gallic acid (3,4,5-trihydroxybenzoic acid) by heating an aqueous solution of gallic acid at elevated temperatures under high pressures. However, the primary source of gallic acid is gall extracts and therefore the availability of gallic acid is quite limited and the costs are quite high.
Another known process for the production of pyrogallol is hydroxylation of catechol or resorcinol with hydrogen peroxide. This technique, however, has been found to be generally unsuitable for technical production. Accordingly, the range of usefulness of pyrogallol has been heretofore limited to applications such as an intermediate for certain pharmaceuticals, an analytical reagent or a reagent for absorption of oxygen, which requires only relatively small quantities of pyrogallol.
A need exists, therefore, for a method of producing pyrogallol and 5-substituted pyrogallol on an industrial scale whereby the costs of production would be drastically cut, thereby permitting these compounds to be used more widely, particularly in the field of agricultural chemicals, pharmaceuticals, dyestuffs and the like.